Article Black Lights for Aquarium Use?

This is actually a popular question that I have been asked many times, and I always give the same answer; that it really isn’t a great idea. The reason using a black-light is a bad idea is because it produces mostly UV light that is damaging to the eyes. You should never stare directly at a black-light, and neither should your fish!

A black-light is essentially a fluorescent bulb that produces light in the 370nm range. 370nm is just barely within our range of visible light, and is quite far into the violet spectrum, producing UVA rays which can potentially be harmful. The benefit is that UV light tends to cause some materials to fluoresce. Many types of paints used on ornaments will fluoresce (or glow) when exposed to some form of UV light. Many living corals produce UV protective pigments that will fluoresce under UV light as well. Unfortunately, black-lights produce too much harmful UV rays to be used practically on aquariums.

Don’t worry; there is an alternative for you! There is another type of bulb that causes the same glowing effects as a black-light, and it isn’t going to cause damage to your fish’s eyes. The bulbs I am referring to are called “actinic”. The word “actinic” describes bulbs that are within the 420nm to 470nm range. These bulbs tend to be purple (when closer to 420nm) to blue (when closer to 470m) in color. They will light up the aquarium more then a black-light would, and will still cause your ornaments to glow. They make actinic bulbs to fit many styles of fixtures, and you should have no problem finding one to fit your aquarium. Actinic bulbs are used mainly in salt water applications, this is because it emulates the deep blue colors of the ocean, and really brings out the colors of fish. Actinic bulbs also produce light that is used by corals for photosynthesis. Although it isn’t uncommon for actinic bulbs to be used in freshwater applications to bring out a desired look to the aquarium, they are actually used quite often on African cichlid aquariums. There is one other option if you have your heart set on a black-light for your aquarium. You can exchange your fish for a species that will not be affected by the UVA rays. There are in fact species of fish and invertebrates that have adapted to living in caves and do not have eyes! Astyanax jordani also known as the Blind Cave Tetra does not have eyes to be damaged by a black-light. These fish are pretty easy to come by, they are not too difficult to keep alive and healthy, and are